Conference key agreement in a quantum network

Alexander Pickston, Joseph Ho, Andrés Ulibarrena, Federico Grasselli, Massimiliano Proietti, Christopher L. Morrison, Peter Barrow, Francesco Graffitti, Alessandro Fedrizzi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Quantum conference key agreement (QCKA) allows multiple users to establish a secure key from a shared multi-partite entangled state. In a quantum network, this protocol can be efficiently implemented using a single copy of a N-qubit Greenberger-Horne-Zeilinger (GHZ) state to distil a secure N-user conference key bit, whereas up to N-1 entanglement pairs are consumed in the traditional pair-wise protocol. We demonstrate the advantage provided by GHZ states in a testbed consisting of a photonic six-user quantum network, where four users can distil either a GHZ state or the required number of Bell pairs for QCKA using network routing techniques. In the asymptotic limit, we report a more than two-fold enhancement of the conference key rate when comparing the two protocols. We extrapolate our data set to show that the resource advantage for the GHZ protocol persists when taking into account finite-key effects.

Original languageEnglish
Article number82
Journalnpj Quantum Information
Publication statusPublished - 22 Aug 2023

ASJC Scopus subject areas

  • Computer Science (miscellaneous)
  • Statistical and Nonlinear Physics
  • Computer Networks and Communications
  • Computational Theory and Mathematics

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